Objective:To evaluate the protection of Ulinastatin(UTI)on pulmonary tissue during cardiopulmonary bypass(CPB). Methods:Twenty-five patients undergoing open-heart surgery under CPB were evaluated in this study. The patients were randomly divided into two groups:control group and experimental group. The experimental group received Ulinastatin as the way of pulmonary protection. Polymorphonuclear neutrophils(PMN) and platelet(Pt) count,interleukin-6(IL-6),interleukin-10(IL-10),tumor necrosis factor-a (TNF-a),alveolar oxygenation index(OI),airway peak pressure and plateau pressure were recorded perioperatively between two groups. Results:The changes of PMN and Pt count in the right atrium blood were significantly higher than that in the left one on 5 min after aorta declamped in control group(P < 0.05). The plasma levels of IL-6 and TNF-a in experimental group were significantly lower than that of the control group(P < 0.05). IL-10 in experimental group increased compared with control group(P < 0.05). OI,airway peak pressure and plateau pressure in control group was significantly higher(P < 0.05) than that of experimental group. Conclusion:Our results demonstrated that PMN and Pt could aggregate in the pulmonary,and IL-6,TNF-a,IL-10 could play an important role in lung injury in CPB. The Ulinastatin could protect pulmonary during cardiopulmonary bypass.